This invention relates to a detection system for receiving incoming signals coming from many different directions and presenting indications of for example the direction and/or range of a source of incoming signals.
Particularly, it relates to a detection system in which a plurality of reception beams are formed successively in angular directions by combining output signals from a plurality of receiving elements positioned at different points on a straight or a curved line, and to an improved detection system of the type, featuring a considerably increased number of reception beams.
The invention can be applied in underwater detection systems such as fish finding apparatuses, radar apparatuses, and direction finders.
Hereinafter, the invention will be explained as embodied in an underwater detection system although as explained above the invention is not limited to that particular system.
A prior art underwater detection system of the type is disclosed in U.S. Pat. No. 3,846,745. The underwater detection system comprises a plurality of ultrasonic transducers equidistantly spaced on a circle, an interpolator for producing interpolated reception signals, a beamformer comprising a plurality of delaying elements each coupled to the transducers through the interpolator, a switching unit for connecting each of the transducers to the interpolator, and an indicator for indicating the output signals of the beamformer. Groups of the transducers are successively selected out of the plurality of the transducers by the switching unit for reception of incoming signals which are transmitted to the beamformer, so that reception beams are formed sequentially in a series of angular directions. However, the prior art underwater detection system has several drawbacks, one of which is that the switching unit needs many switches to properly successively selected predetermined groups of the transducers, thus making the interconnections between the switches and transducers complicated, another drawback being that the switching unit produces noises when switching operations are performed.
Accordingly, an object of the present invention is to provide a detection system which is constructed on a novel conception.
Another object of the invention is to provide an underwater detection system which is constructed in a small size by considerably reducing the number of the switches.
Another object of the invention is to provide an underwater detection system free from switching noises.